I've got reference 7900xt from PowerColor running on Linux. It's installed in a pretty old ThreadRipper 1950X system with ReBAR support, so some of the issues below might be related to an old platform rather than the GPU.
There are problems with the kernel driver, unfortunately, when using 2+ 4k monitors. They are working on them but right now I would not recommend using a mainline kernel for that purpose. I am managing with a custom kernel but sometimes there are hangs (not often).
The userspace driver - mesa - is great, though. They recently worked on aco (the Vulkan (and OpenGL in the future) shader compiler) support for VOPD (dual-issue on RDNA3), but even without it when you default to wave64 the hardware uses the dual-issue capability (with the possible occupancy problems inherent to wave64, applied).
Thanks to the kernel problems I understand the issues with high idle power usage on navi31 in general. The hardware supports memory reclocking for up to two displays but not more - you should not expect lower idle usage for 3+ monitors due to hardware limitations. Even with just 2 monitors there are issues as the hardware tries not to disturb the display as it tries to change the clock during vblank (?). This might also cause problems with high refresh rates (240Hz+).
It's possible these problems are all already fixed with the Windows driver, except the 3+ monitor idle power usage. I can be proven wrong, though.